Next to each other as separate buttonsAlways available to press (no "go" button)

Firefox 3.6

Refresh and cancel are on the right of the addressNext to each other as separate buttons

Always available to press (no "go" button)

Firefox 3.6 loading

Spinner in the tab, now refresh and cancel are both available

Chrome 5

Single refresh button on the left of the addressA "go" button exists

Chrome 5 loading

Spinner in tab, now the "go" is a cancel button

I do not use the "go" button ever, instead rely more on the reload and back/forward buttons, therefore I find it inconvenient that the "cancel" is so far away and out of place compared to those buttons.

Spinner and text in address bar, entire region is a cancel button. Cancel in same place as the refresh, easy to click now as opposed to the initial refresh button

Summary

Chrome's layout is too spread out and the least user-friendly in these regards. Safari gets the loading part right (clear indication of loading, nice call to action to cancel and try again). Overall, Safari is the only one to optimize for the "cancel and retry" action, which I find myself doing a lot when a site is struggling to load due to Internet connectivity issues or DNS hiccups.. however the initial refresh button is a bit small.

Update (11-2010): Chrome 7 updated the interface on the Mac and addressed my usability concerns. There is no longer a "go" type button, so that matches the other browsers, and more importantly the cancel button is the same as the refresh now.. so no more back and forth all the way across the interface when trying to stop and reload a non-responsive site.